package top.fengleifeng.question;

import java.util.HashMap;
import java.util.Map;

/**
 * @program: leetcode-test
 * @description:
 * 剑指 Offer 20. 表示数值的字符串
 * 请实现一个函数用来判断字符串是否表示数值（包括整数和小数）。例如，字符串"+100"、"5e2"、"-123"、"3.1416"、"-1E-16"、"0123"都表示数值，但"12e"、"1a3.14"、"1.2.3"、"+-5"及"12e+5.4"都不是。
 *
 *
 *
 * 通过次数37,222提交次数161,007
 * 在真实的面试中遇到过这道题？
 * @author: fengleifeng
 * @create: 2020-10-09 11:39
 **/
public class Y剑指Offer20表示数值的字符串 {
    /**
     * 状态机实现
     */
    class Solution {
        public boolean isNumber(String s) {
            Map<State, Map<CharType, State>> transfer = new HashMap<State, Map<CharType, State>>();
            Map<CharType, State> initialMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_SPACE, State.STATE_INITIAL);
                put(CharType.CHAR_NUMBER, State.STATE_INTEGER);
                put(CharType.CHAR_POINT, State.STATE_POINT_WITHOUT_INT);
                put(CharType.CHAR_SIGN, State.STATE_INT_SIGN);
            }};
            transfer.put(State.STATE_INITIAL, initialMap);
            Map<CharType, State> intSignMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_INTEGER);
                put(CharType.CHAR_POINT, State.STATE_POINT_WITHOUT_INT);
            }};
            transfer.put(State.STATE_INT_SIGN, intSignMap);
            Map<CharType, State> integerMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_INTEGER);
                put(CharType.CHAR_EXP, State.STATE_EXP);
                put(CharType.CHAR_POINT, State.STATE_POINT);
                put(CharType.CHAR_SPACE, State.STATE_END);
            }};
            transfer.put(State.STATE_INTEGER, integerMap);
            Map<CharType, State> pointMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_FRACTION);
                put(CharType.CHAR_EXP, State.STATE_EXP);
                put(CharType.CHAR_SPACE, State.STATE_END);
            }};
            transfer.put(State.STATE_POINT, pointMap);
            Map<CharType, State> pointWithoutIntMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_FRACTION);
            }};
            transfer.put(State.STATE_POINT_WITHOUT_INT, pointWithoutIntMap);
            Map<CharType, State> fractionMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_FRACTION);
                put(CharType.CHAR_EXP, State.STATE_EXP);
                put(CharType.CHAR_SPACE, State.STATE_END);
            }};
            transfer.put(State.STATE_FRACTION, fractionMap);
            Map<CharType, State> expMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_EXP_NUMBER);
                put(CharType.CHAR_SIGN, State.STATE_EXP_SIGN);
            }};
            transfer.put(State.STATE_EXP, expMap);
            Map<CharType, State> expSignMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_EXP_NUMBER);
            }};
            transfer.put(State.STATE_EXP_SIGN, expSignMap);
            Map<CharType, State> expNumberMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_NUMBER, State.STATE_EXP_NUMBER);
                put(CharType.CHAR_SPACE, State.STATE_END);
            }};
            transfer.put(State.STATE_EXP_NUMBER, expNumberMap);
            Map<CharType, State> endMap = new HashMap<CharType, State>() {{
                put(CharType.CHAR_SPACE, State.STATE_END);
            }};
            transfer.put(State.STATE_END, endMap);

            int length = s.length();
            State state = State.STATE_INITIAL;

            for (int i = 0; i < length; i++) {
                CharType type = toCharType(s.charAt(i));
                if (!transfer.get(state).containsKey(type)) {
                    return false;
                } else {
                    state = transfer.get(state).get(type);
                }
            }
            return state == State.STATE_INTEGER || state == State.STATE_POINT || state == State.STATE_FRACTION || state == State.STATE_EXP_NUMBER || state == State.STATE_END;
        }

        public CharType toCharType(char ch) {
            if (ch >= '0' && ch <= '9') {
                return CharType.CHAR_NUMBER;
            } else if (ch == 'e' || ch == 'E') {
                return CharType.CHAR_EXP;
            } else if (ch == '.') {
                return CharType.CHAR_POINT;
            } else if (ch == '+' || ch == '-') {
                return CharType.CHAR_SIGN;
            } else if (ch == ' ') {
                return CharType.CHAR_SPACE;
            } else {
                return CharType.CHAR_ILLEGAL;
            }
        }


    }


}
enum State {
    STATE_INITIAL,
    STATE_INT_SIGN,
    STATE_INTEGER,
    STATE_POINT,
    STATE_POINT_WITHOUT_INT,
    STATE_FRACTION,
    STATE_EXP,
    STATE_EXP_SIGN,
    STATE_EXP_NUMBER,
    STATE_END,
}

enum CharType {
    CHAR_NUMBER,
    CHAR_EXP,
    CHAR_POINT,
    CHAR_SIGN,
    CHAR_SPACE,
    CHAR_ILLEGAL,
}